Beware! Nancy Pelosi is a colossal tax-dollar-engorged monster who ravages small towns and must be brought down by Republican ray guns. Or at least that is what a cartoon version of the House speaker looked like in "Attack of the 50-Foot Pelosi," a television ad that a conservative group called Right Change aired in Pennsylvania last month.

A new Web site by the National Republican Congressional Committee portrays her as a malevolent puppet master, yanking the strings of 10 vulnerable House Democrats.

And a video on the campaign home page of GOP House candidate Harold Johnson of North Carolina makes her sound like someone out of those creepy cable ads for burglar alarms. "If you're a small-business owner," Johnson says, "you get up every morning and you put your helmet on, because you think that Nancy Pelosi is going to come into your bedroom and hit you over the head with a baseball bat."

This is the kind of problem that J. Dennis Hastert, Carl Albert and Frederick Gillett never had to deal with. House speakers, with a few exceptions, have been such colorless legislative insiders that the mention of their names in most of America would have received no reaction beyond quizzical looks.

Not this year, and not this speaker. "If you go to almost any grass-roots event and you mention the speaker's name," said Bill Flores, a Republican who is challenging Rep. Chet Edwards (D-Tex.), "you will get a huge response from the audience." Which is why, by Flores's estimate, he manages to drop Pelosi's name into his speeches about as often as he does President Obama's.

Pelosi (D-Calif.) has become "the face of liberalism in the Obama era," more so than Obama himself, said Julian E. Zelizer, a professor of history and public affairs at Princeton.

Her infamy among conservatives is partly the product of her often-imperious manner, a rougher media culture and a superheated political climate. But it is also a backhanded acknowledgment of how effective she has been.

Pelosi has unabashedly wielded the leverage of her office to muscle her agenda through the House. Once dismissed by her opponents -- and even some of her fellow Democrats -- as a lightweight, she has proved to be "the most powerful speaker we've seen in modern history," said political analyst Charlie Cook, whose assessment is shared by a number of congressional scholars.

More questionable is whether making Pelosi the bogeywoman of this year's congressional elections will help Republicans win back the House.

A Washington Post-ABC News poll conducted in late March, around the time that the speaker engineered the final passage of health-care overhaul in the House, suggested that she stirs both sides.

Pelosi's overall approval ratings had not changed much over the previous three months, but the partisan passion that surrounded her had grown more intense. Among Republicans, the number who "strongly disapprove" of her performance jumped from 60 percent to 74 percent, which was greater than their negative view of Obama. But there was a corresponding rise in her approval among Democrats: Thirty-eight percent "strongly approved" of her performance as speaker in late March, up from 22 percent in mid-January.

So when the Republican National Committee unfurled a big red "FIRE PELOSI" banner last month from a window of its Capitol Hill headquarters, right above the front door, the Democratic Congressional Campaign Committee sent out a photo of it in its own fundraising e-mail.

"Fire Pelosi" became a GOP rallying cry 15 minutes after the health-care vote, when the RNC launched a Web site depicting the speaker engulfed in flames and brandishing her fist. The Republicans say that one appeal raised $1.5 million in less than a week; Democrats called upon her supporters to come up with at least $1 million in response.

When Pelosi is asked about the starring role she is playing in this year's campaign, she dismisses it. "I think mostly people are interested in what the comparison is between the candidates," she said. "Let them do what they do."

Indeed, making an issue of the speaker is not exactly a new idea.

As far back as the 1980 presidential campaign, Republicans aired a television ad that depicted a car running out of gas. Behind the wheel was a beefy, white-haired actor who looked a lot like Tip O'Neill (D-Mass.). "He really has an Irish kisser," the then-speaker said of his doppelganger.

Newt Gingrich's staff estimated that his name or image popped up more than 100,000 times in campaign advertising during his stormy four-year tenure.

"It can become really demoralizing for your side," the Georgia Republican said. The current effort against Pelosi, he added, "weakens her in her own caucus, as it certainly weakened me in my own conference."

But did their assault on Gingrich win the Democrats any seats? "No," said Steve Elmendorf, who was the top aide to then-House Democratic leader Richard A. Gephardt (D-Mo.). "It's very hard in any of these races to make it about the congressional leadership."

And Gingrich warned that campaigning against the Democrats -- even one as unpopular with Republicans as Pelosi -- is no substitute for offering voters some idea of how the GOP would govern if Republicans won back the House. "People who think that all the Republicans should do is just yell 'no' are just plain wrong," he said.